I recently received and tested the first 1.8V Ethernet FMCs and they are now available to buy on ethernetfmc.com. There are two main reasons why you’d actually want a 1.8V version: Firstly, some carriers only support VADJ of 1.8V (such as the VC707 and VC709). Secondly, some customers need to match it with another 1.8V FMC on a dual-FMC carrier.

Releasing the new version didn’t come without headaches. Most FMC carriers on the market have a 2.5V VADJ by default, so there’s a good chance of frying the Ethernet PHYs on first go. Luckily I haven’t made that mistake yet! The other “problem” is the fact that the board provides a 125MHz LVDS clock – respecting the Vita 57 standard – but creating a problem for carriers with FMCs that route to HR (high-range) banks. Which is most of them! Yes the ZedBoard, AC701, KC705, ZC702 and ZC706 all route to HR banks. HR banks require you to define your LVDS I/Os with the LVDS_25 IO standard (ie. the 2.5V standard), but we’d really want to be using the LVDS (1.8V) IO standard. So I had to either declare non-compatibility or find a workaround. Fortunately, there is a workaround and I’ve written about it here:

Using the 1.8V version Ethernet FMC with the ZedBoard

So if you need an Ethernet FMC that works at 1.8V, now you can have it!


Jeff is passionate about FPGAs, SoCs and high-performance computing, and has been writing the FPGA Developer blog since 2008. As the owner of Opsero, he leads a small team of FPGA all-stars providing start-ups and tech companies with FPGA design capability that they can call on when needed.

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